1. Field of the Invention
The present invention relates to a wireless device, and more particularly, to a removable wireless device with a compact antenna design and improved thermal dissipation characteristic.
2. Description of the Prior Art
A removable wireless device, such as USB (Universal Serial Bus) device, is useful to expand or upgrade portable equipment with functionality that the portable equipment does not have. For example, a Wi-Fi USB dongle can help a notebook access to wireless local area network (WLAN); while a BT (Bluetooth) USB dongle can help the notebook connect with other peripheral devices. In another example, if the notebook is originally equipped with a legacy WLAN device, such as those compatible with IEEE802.11a/b/g, using an IEEE 802.11n USB dongle can easily upgrade the wireless connection capability of the notebook.
However, the removable wireless device often extrudes from the portable equipment and interferes with the user when using the portable equipment. A common method to reduce the size of the removable wireless device is to change the design of the antenna. FIG. 1 to FIG. 3 illustrates different type of antennas used in a WLAN USB dongle. The antenna 102 in FIG. 1 is a printed antenna laid on the substrate 103 and coupled to the ground plane 101. The printed antenna 102 has to be thin and meandered so as to achieve a required physical length such as quarter wavelength of a desired frequency band, for example. However, this high density layout may cause large impedance and make time-variable currents thereon be eliminated with each other. Besides, the large area that the printed antenna occupies is another concern.
The antenna 202 in FIG. 2 is a metal folded 3-dimensional antenna set up on the substrate 203. The disadvantage of the antenna 202 is that precision of manufacturing such kind of antenna is low. Using this kind of antenna also increases the size of the wireless device since the antenna has to be expanded in the three dimensional space to reach the desired physical length.
FIG. 3 illustrates a conventional chip antenna 302. The chip antenna 302 is disposed on the substrate 303, and coupled to the ground plane 301. The chip antenna 302 reduces the size of the antenna, but increases the cost of the antenna and has low antenna efficiency and low peak gain in a small ground plane.
Therefore, it is still difficult for those skilled in the art to have an antenna design with high efficiency, compact size and low cost in a removable wireless device.
In addition, when the size of the wireless device is reduced, there's less area to dissipate heat. Moreover, a dense arrangement of the chips and components also increase the amount of heat generated inside the wireless device. Therefore, there's also a need to provide a compact wireless device with an improved thermal dissipation characteristic.